Local patrols by steelworkers have forced pro-Russia insurgents to retreat from the government buildings they had seized in a major city in eastern Ukraine, giving residents hope that a wave of anarchy was over.

In a report Friday, the United Nations raised concern about the increasing human rights abuses in eastern Ukraine as armed groups took advantage of the breakdown in law and order.

Mariupol is the second-largest city in Ukraine's eastern Donetsk region — one of two regions that declared independence Monday from the central government in Kyiv. Citizen patrols began there earlier this week as Rinat Akhmetov, Ukraine's richest man, urged steelworkers at his factories to help police restore order.

On Thursday, Akhmetov's company, Metinvest, agreed with steel plant directors, police and community leaders to help improve security in the city and get insurgents to vacate the buildings they had seized. A representative of the self-proclaimed Donetsk People's Republic, which had declared independence, was also a party to the deal.

Metinvest has two steel plants Mariupol, a city of half a million people. The port and industrial centre lies on the main road between Russia and Crimea, the peninsula annexed by Moscow in March. The city saw heavy fighting in the past weeks, including a shoot-out outside a police station that left one policeman and several insurgents dead. Without the city, Ukraine would lose a chunk of its coastline on the Sea of Azov, which links to the Black Sea.

The Associated Press journalists did not see any insurgents Friday morning in the city.

German Mandrakov, once the commander of Mariupol's occupied government building, told The Associated Press on Friday that his associates fled while he was "forced" to leave the building they had controlled for weeks.

"Everyone ran away," he said, using a vulgar Russian word for cowards. "Someone is trying to sow discord among us, someone has signed something, but we will continue our fight."

'Tired of war and chaos'

Several dozen Metinvest workers in overalls and helmets cleared out barricades of rubbish and tires outside the Mariupol government building Friday. Trucks carried it away and by midday, the barricades were nearly gone.

"[Locals are] tired of war and chaos. Burglaries and marauding have to stop," said ViktorGusak, one of the Metinvest employees cleaning the street.

A pro-Russian rebel surveys an area on the outskirts of the eastern Ukrainian town of Slovyansk on Thursday. (Yannis Behrakis/Reuters)

A few hundred metres away, three men sat in the park cooking soup. One of them, unemployed Serhiy Atroshchenko, told the AP they were all that was left of Mariupol's pro-Russian separatist force.

"We were duped," Atroshchenko said. "Akhmetov used to keep his eyes closed (to what was happening), but now he decided to make a deal with Kyiv authorities."

Atroshchenko said other separatists fled and only he and his two friends —the "men of ideas," he claimed — were left "to fight till the end." None of them was armed.

While groups of armed men were seizing one town hall after another in eastern Ukraine, a region widely believed to be Akhmetov's turf, the billionaire industrialist kept mum, attracting angry comments across the country.

Among the graffiti aimed at Akhmetov in Kyiv was this: "Want to make money? First, make some peace!"

On Wednesday, Akhmetov broke his silence to call for Donetsk to remain part of Ukraine, arguing that independence or absorption into Russia would be an economic catastrophe.

Since President Viktor Yanukovych's ouster in February, Ukraine's new leadership has reached out to oligarchs for help — appointing them as governors in eastern regions where loyalties to Moscow were strong.

Police, steelworkers patrol together

Ihor Kolomoisky, a metals, banking and media tycoon who was appointed governor of his native region of Dnipropetrovsk, was among those praised for preserving order. Others like industrialist Serhiy Taruta, governor of the Donetsk region, seemed helpless as district after district fell into the insurgents' hands.

In Mariupol, the first major citizen patrol sponsored by Akhmetov's Metinvest was held Thursday, police spokeswoman Yulia Lafazan said. There are now about 100 groups of men consisting of two policemen and six to eight steelworkers patrolling Mariupol.

A pro-Russian militant rests at a checkpoint outside Slovyansk in eastern Ukraine. The armed separatists installed a new check-point on the eastern approaches of the city to block the major highway that links Kharkiv. (The Associated Press)

Lafazan credited the patrols for a "drastic improvement" in the city's crime rate.

Burglaries and carjackings became the norm after the pro-Russia insurgents asserted themselves earlier this month, bringing in a wave of marauding, she said, adding that carjackings have ceased since the patrols began.

"For the first time (in weeks), I can go out shopping without fear," said local resident 47-year-old Valentyna Tochilina.

In other areas in eastern Ukraine, however, the pro-Russia insurgents were fortifying their territories.

Outside the strategic city of Slovyansk, an insurgent stronghold for more than a month now, armed separatists installed a new checkpoint on the eastern approaches to the city. That checkpoint blocks a major highway that links Kharkiv, Ukraine's second-largest city — with the Russian city of Rostov-on-Don across the border.

Associated Press journalists saw several dozen heavily armed men fortifying the new checkpoint with concrete slabs, helped by some local residents.

In Kyiv, Ukraine's acting President Oleksandr Turchynov on Friday urged residents of the eastern regions to stop helping the separatists and support the central government.

"You've got to support the anti-terrorist operation so that we could defeat terrorists and separatists in Donetsk and Luhansk regions together," he told the parliament. "The actions of the terrorists are threatening lives and welfare of the people."